The U.S. Pat. No. 4,851,618 A discloses a computer keyboard in which a key holding frame is attached to a base plate comprising electrical circuits by a plurality of hooks and posts engaging with holes in the base plate.
The U.S. 2004/031673 A1 relates to a particular design of a keypad comprising both elevated and not-elevated regions which are separately evaluated by a particular algorithm. The keypad includes a keymat that is rigidly held at its perimeter in a stretched condition across a switch substrate.
The EP 1 876 620 A1 relates to a remote control in which several components are aligned to a common housing.
Due to current product and design requirements more and more devices require input key-mat with press buttons close to each other and close to the edge of an input device.
Parts of a portable device are typically aligned to the (top and/or bottom part of) housing of the device, e.g., by hooking to the housing. This housing typically comprises a plastic injected part with higher tolerances. The key-mat and housing need to be properly aligned for visual and functional requirements and this result e.g., in gaps which are a compromise between avoiding ‘sticking’ key-press/buttons and small optical gaps. Also, tolerances between the press buttons are high because they are aligned towards the housing and/or the key-mat is from a rubber material with inherent high tolerances.
For a small key-mat above mentioned hooking and aligning to top and/or bottom part is feasible. However for a bigger key-mat, such as in a remote control, the hooking and aligning is less feasible, e.g., due to plastic molding tolerances. Moreover no provision for a modular design of the key-mat is available.